European hydraulic geometries for continental SCALE environmental modelling

This paper presents a geo-exploratory analysis carried out using publicly accessible data to estimate river channel width and mean lake depth. These two parameters, combined with other more readily available information, are key in many environmental assessment applications such as sedimentological and ecological studies, and the prediction of surface water residence times. For river width, runoff estimates have been used to produce a European map of mean annual discharge based on the flow accumulation computed for the GTOPO30 digital elevation model (DEM). A regression equation is fitted to predict river width as a function of river discharge. For lake depth, a landscape roughness index has been calculated on the GTOPO30 DEM. Based on this index, a regression equation predicts lake depth, allowing to populate the existing geographic databases with information on estimated depth. Using these models for river width and lake depth it is possible to compute “representative” values of velocity and depth in rivers, as well as residence time in lakes at a pan-European level. These parameters define the hydraulic geometry of European inland waters for typical conditions with errors on the predictions generally within a factor of 2. Errors are generally unbiased, and geographic patterns (such as macroscopic differentiation of catchments and physiographic environments) are reproduced in a qualitatively correct way, so that overall representativeness of the values for continental scale modelling is further corroborated.